Multiposition magnetically held fail-safe switch

ABSTRACT

A concept of multiposition magnetically held fail-safe switching employs a control solenoid for each successive pair of switch positions. Each solenoid effects both holding and blocking functions under control of an associated logic-enabled energization source to achieve fail-safe operation with minimal complexity, cost, and power consumption.

United States Patent Inventor David W. Ellis Costa Mesa, Calif. Appl. No. 69,072 Filed Sept. 2, 1970 Patented Oct. 19, 197 l Assignee Collins Radio Company Cedar Rapids, Iowa MULTIPOSITION MAGNETICALLY HELD FAIL- SAFE SWITCH Primary Examinerl-larold Broome Attorneys-Richard W. Anderson and Robert .1. Crawford ABSTRACT: A concept of multiposition magnetically held fail-safe switching employs a control solenoid for each successive pair of switch positions. Each solenoid effects both holding and blocking functions under control of an associated logic-enabled energization source to achieve fail-safe operation with minimal complexity, cost, and power consumption.

12 Claims, 11 Drawing Figs.

US. Cl 335/167, 74/527, 335/74 Int. Cl H0111 9/20 Field of Search. 335/167 (169),190,173,74,136,192;200/l53, 9; 74/527, 528, 529

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DAVID W. ELL/S AGENT MULTIPOSITION MAGNETICALLY HELD FAIL-SAFE SWITCH This invention relates generally to switching means and more particularly to a magnetically controlled fail-safe switch the positions of which are attainable only if predetermined logic controlling the energization of controlling solenoids is realized and which automatically disengages to a predetermined position in the event of logic failure or system power failure.

By way of exemplification and not limitation, the switch of the present invention will be described as it applies to engaging an aircraft automatic pilot control system to predetermined operational functions wherein engagement in one or more control functions is permitted only if predetermined logic associated with that function is present (as by arming pulses), and wherein loss of logic for a given position or function effects automatic progression towards home or off position to the next energized or logically enabled position.

Two-position magnetically held switches of a type known in the art employ spring loaded arms including pole pieces which are magnetically latched by an energized coil when the switch is in the engaged position. Deenergization of the coil causes the switch arm to be urged towards the home or off position by spring return means. These types of switches are generally not applicable to a fail-safe embodiment for reasons which will be later discussed in detail and briefly mentioned here as being so constructed as to permit momentary engagement of the switch into the control position whether or not the coil is energized. Thus these types of known switches permit a momentary tumon when the operator attempts an engagement whether or not the logic associated with the coil is present or not. Further, known magnetically held switches are not adaptable to multiposition operation, that is, three or more positions.

The momentary engagement possibilities of known magnetically held switches might be obviated by the inclusion of a second coil to control a mechanical blocking linkage to prevent progression of the switch position from the home position to control position unless logic associated with the blocking solenoid is present. The elimination of certain undesirable features and limitations of the basic single solenoid magnetically held switch may be overcome by the addition of a second solenoid which controls necessary blocking functions. However, these methods increase complexity, cost, and power consumption, and decrease reliability, since, generally, failure of either solenoid coil is not recognized by the other and, should holding coil fail, the blocking oil will permit operation of a faulty switch. Conversely, if the blocking coil fails, the blocking function is lost. Thus the inclusion of dual solenoids to respectively function as holding and blocking control solenoids falls short of the ideal approach to a magnetically held fail-safe switch.

Accordingly, the object of the present invention is the provision of means to attain completely fail-safe magnetic hold and blocking functions in a multiposition control switch with minimum complexity, cost, and power consumption.

A further object of the present invention is the provision of a multiposition magnetically held switching concept readily adaptable to changing design criteria and switching require ments.

Still another object of the present invention is the provision of a actuated multiposition switch which may be deactuated either manually or automatically by deenergization of logic controlled holding coils.

A further object of the present invention is the provision of a multiposition magnetically control switch wherein mechanical latching aspects prevent switch position progression to the next upward position from home without appropriate controlling solenoids being energized.

Another object of the present invention is the provision of a magnetically controlled multiposition switch so constructed that loss of logic power to an appropriate solenoid when the switch is engaged in a particular control position effects switch disengagement and a flyback to the immediately preceding logically energized position.

A still further object of he present invention is the provision of a magnetically held multiposition switch wherein solenoid holding power consumption is minimal and return to home or off position is rapidly effected with loss of holding power.

The present invention is featured in the incorporation of a logic controlled solenoid member for each successive sixth pair of a multiposition switch. A control plate rotatable with the switch shaft is formed with locking means which cooperate with the solenoid plunger positions such that each solenoid combines blocking and holding functions in a predetermined manner to effect e aforedet'med operational objectives.

These and other features and objects of the present invention will become apparent upon reading the following description with reference to the accompanying drawings in which;

FIGS. 1(a) and 1(b) depict operational characteristics of known two-position magnetically held switches;

FIG. 2 depicts a design improvement for incorporation with the basic device of FIG. 1 by means of which position blocking functions may be added to the basic concept;

FIGS. 3(a), 3(b), and 3(c) depict operational charactei'istics for an improved two-position magnetically controlled switch in accordance with the present invention and FIGS. 4(a)-4(e) represent respective progressive switch positions from home to a last control position of a three-position switch designed in accordance with the present principles of the present invention.

The present invention will herein be described in the context of its application to automatic pilot engage switch operations. While two and three-position embodiments of a fail-safe magnetically controlled switch in accordance with the inventive principle will be considered in detail, the design concept of the present invention permits ready adaptation to solenoid held switch applications requiring more than three positions by the incorporation of appropriate numbers of solenoids and cooperating latching means.

The following operational characteristics might typically be required for a three-position autopilot switching means which is to incorporate fail-safe features. The term fail-safe as used here pertains to the ability of the switch to instantly return to a predetermined home position upon loss of energizing power and/or certain logic generated controlled power sources which control the switch's ability to position in and maintain certain functional positions.

1. Switch to be actuated manually and actuated either manually or by deenergization of holding coils under the control of logic circuitries.

2. Mechanical latching will prevent progression to the next upward position away from home position until an appropriate associated solenoid coil is energized. I

3. When the switch is engaged in some position other than home position, the switch shall rapidly disengage and immediately drop to the immediately preceding energized position when power to an appropriate solenoid coil is removed.

4. Should all power fail, the switch shall rapidly drop to the off or home position.

5. The switch may be manually disengaged with all coils energized by an override feature.

6. Should the switch contacts weld due to abnonnally large current loads, the switch shall provide a direct mechanical link through which these welded contacts may be manually broken.

7. The switch shall provide an adequate center position detent which will not interfere with this engagement when the holding coils are deenergized.

From the above it is seen that autopilot engagement into a given function is permitted only if arming logic associated with that function of the autopilot indicates operability. Once engaged the switch shall automatically disengage the autopilot should control logic or power be lost. The disengagement" in certain applications might means flyback from one engaged function to a next proceeding function toward the home position or off position where progression to switch positions away from home engage functions which are operationally dependent on respective higher degrees of sophistication as concerns operational logic. It is generally imperative that any automatic pilot engage switch rapidly disengage the autopilot from any operational function should there be a power loss. These provisions are in the interest of safety.

The present invention uniquelyprovides a versatile design concept for magnetically controlled multiposition switches which might be employed in automatic function engaging operations. The concept permits simplicity of design, economy of operation as concerns power requirement, and complete fail-safeness as concerns holding and disengage functions.

Known prior art magnetically controlled switches and/or design extensions thereof either fail to meet the above enumerated design objectives or meet same at the expense of increased complexity, cost, and power consumption, coupled with a decrease in the reliability of the unit. As such, known expedients and extensions thereof are not readily applicable to the fail-safe requirements of current design objectives.

A known prior art magnetically held switch is depicted in FIGS. 1(a) and 1(b). This switch is a two-position (ON and OFF) device comprised of an arm keyed to the shaft of a rotary wafer switch 11 so as to effect a pivot point 16. Switch 11 is manually positionable between ON and OFF positions by means of handle 12 and is spring loaded into the OFF position by means of a return spring 13. Magnetic coil provides a magnetic latch function. When coil 15 is energized, movement of the handle 12 toward the ON position causes the return spring 13 to become stretched as the striker 14 on arm 10 moves to engage the coil poles of coil 15. the striker l4 closes the The path for the magnetic flux through the coil. Thus this switch is held in the ON position (FIG. 1(

With the switch held in the magnetically controlled ON position as depicted in FIG. I(b), deenergization of the coil 15 allows the switch flyback to the OFF position by the return spring 13. When an engage attempt is made (positioning from OFF and ON) with coil 15 deenergized, the switch may be moved to the ON position, but it will not hold in this position. However, a momentarily ON engagement is made during the time period that switch 11 is manually held in this position.

The switch of FIGS. 1(a) and 1(b) is accordingly not only unadaptable to other than two-position embodiments, but additionally possesses inherent disadvantages as concerns failsafe switch requirements for a two-position design. Firstly, in most applications using a magnetically held switch, it is desirable to prevent the switch from being turned on when the coil is deenergized. The switch of FIG. 1 may be turned on momentarily whenever the operator attempts an engage whether the coil 15 is energized or not. Further, concerning the switch of FIG. 1, the operator has no way of knowing whether or not the coil 15 is energized until he moves the handle 12 through its entire travel. There is no mechanical movement present which could be used to supply such information.

The disadvantages of the basic magnetically held switch embodiment of FIG. 1 could be eliminated by a design extension which provides a mechanical movement which would block progression of handle 12 when the solenoid is unenergized. This function might, for example, be provided by adding a further coil as functionally depicted in FIG. 2. The switch would then comprise two coils, one used for a holding function (as in FIG. 1(b)) and the other coil (coil 22 of FIG. 2) used for blocking progression to successive positions in the absence of blocking coil energization.

The side view of FIG. 2 depicts the pivot point 16 of a rotary switch as shown in FIG. 1 together with three switch positions identified as OFF, CWS and CMD. The handle of the switch extends through an opening in a plate 20. The additional blocking solenoid 22 is depicted in an energized position such that the solenoid shaft positions a blocking linkage 23 out of engagement with the handle lever 10. permitting progressive switch positions from the OFF position. The linkage 23 is urged into a blocking position (not illustrated) by means of return spring 25. Thus, in the event that the blocking coil is deenergized the linkage 23 pivots to present a mechanical impediment to progessive switch positions from the OFF position. However, the method of adding the second coil of FIG. 2 to the basic holding function of FIG. I increases the complexity, cost, and power consumption of the unit and, in addition, decreases the reliability. Failure of either the holding or the blocking coils is not recognized by the other coil. If the holding coil fails, the blocking coil will allow operation of a faulty switch. If the blocking coil fails, the blocking function is lost.

In accordance with the present invention, the problems inherent with known devices or extensions thereof may be solved by combining the holding and blocking functions with both functions being performed by a single solenoid. In general, one such single solenoid will be associated with each successive pair of switch positions including OFF position. Reference is made to FIG. 3 wherein a two-position design in accordance with the present invention is illustrated.

The two-position fail-safe switch embodiment of FIG. 3, in employing a single pair of switch positions (ON and OFF), utilizes a single solenoid to perform dual holding and blocking functions. In FIG. 3(a) the switch activating arm 10 is shown extended through an opening in a panel 20 and terminated by handle 12. The switch pivot point 16 is depicted functionally as being keyed to the shaft of a rotary switch 37 which, in turn, is functionally depicted as acting on a controlled device 38. Device 38 might be an autopilot control circuitry from which engage logic power is applied on line 39 to the solenoid 36 when the controlled device is operational. The switch arm 10 is attached to, or intricately formed as a part of, a control plate member 30 into which is formed an arcuate through-slot 31. The plunger 34 of solenoid 36 is slotted on the end. A pin member 35 is located crosswise to the slot and this forms a clevis arrangement extending through the slot in control plate 30. The slot 31 is formed with first and second ramplike protrusions 32 and 33 which might generally be defined as inclined plane configurations protruding from the respective sides of slot 31.

Manual positioning of the switch handle 12 from OFF to ON position effects predetermined relationships between the ramp members 32 and 33 and the transverse pin member 35 formed in the plunger 34 of the solenoid, depending upon the energization state of the solenoid 36. The solenoid 36 in FIG. 3(a) is illustrated in energized position with plunger member 34 withdrawn into the solenoid body. The plunger transverse pin member 35 is then in operative engagement with the righthand portion of the control slot 31. Return spring 13 urges the control plate 30 into the OFF position illustrated in FIG. 3(a). With solenoid 36 energized as depicted, the switch may be rotated from the OFF to the ON position since transverse pin 35 on solenoid plunger 34 is free to ride up the inclined surface of ramp 32 and into a detent terminating the upper portion of the through-slot. The switch will be held in the ON position as long as solenoid 36 is energized since the pin cooperating side of projection 32 forms a detent.

A mechanical blockage to movement of the switch from the OFF to the ON position is provided should the solenoid 36 be in the deenergized position with solenoid arm 34 extended such that pin 35 catches against the steeply inclined surface of ramp 33. Should the switch be in the ON position will pin 35 detented by ramp 32, deenergization of solenoid 36 positions pin member 35 into cooperative engagement with the side of the slot containing ramp 33 the inclined surface of which permits flyback to OFF position. Ramplike production 32 is formed, as depicted in FIG. 3(a) with an overridable inclined surface over which solenoid pin member 35 may pass when the switch is progressed from OFF towards ON position, and is formed with a more steeply inclined terminal surface which is designed to provide a manually overridable detent which holds switch in ON position as long as solenoid 36 is energized. Ramp 33 is likewise formed with a gently inclined surface to permit rapid flyback from ON to OFF position should solenoid 36 be deenergized, and with a steeply inclined catch surface to prevent progression from OFF to ON should the solenoid 36 be deenergized.

The operation of the two-position switch embodiment is depicted in FlGS. 3(a)-3(c) in progressive switch positions from the OFF POSITION to the ON position. This operation is summarized as follows;

1. If the solenoid 36 is deenergized 3(b)), a solenoid return spring located inside the solenoid (not illustrated) urges the plunger 34 outward away from the solenoid 36. Progression from ON to OFF is blocked since ramp 33 serves as a catch as it is moved to encounter the transverse pin member 35.

2. When the solenoid 36 is energized (FlG. 3(a)), the plunger 34 is pulled inward toward the solenoid against the compression spring. Progression of the switch is allowed because pin 35 now misses ramp 33. Pin 35 rides over ramp 32 and is held in the ON position as depicted in FIG. 3(0).

3. Ifsolenoid 36 is deenergized while the switch is in the ON position as depicted .in FIG. 3(a), the solenoid releases the catch engagement between transverse pin member 35, and ramp 32 is released, and the switch snaps to the OFF position depicted in FIG. 3(a).

The important advantage of the two-position fail-safe switch illustrated in FIGS. 3(a) through 3 (c) may be summarized as follows:

1. Holding and blocking functions are performed by a single solenoid.

2. Should they be desirable or required, flags or other type of enunciators may be driven directly from the solenoid.

3. The holding power required of the solenoid is small because of the favorable mechanical advantage designed into the ramps 32 and 33. During pull-in the solenoid has only to move its plunger and return spring, thus very fast solenoid pull-in response time is achieved. Force-displacement requirements of the solenoid are optimized allowing the use of a small, low power solenoid.

4. Solenoid disengage movement is not only accomplished by the solenoid return spring but is also aided by the handle return spring 13 via the holding ramp. The plate of the mechanism accelerates rapidly and very fast switch disengage response times result.

5. Should the switch contacts weld or the solenoid plunger bind, the switch can be manually overridden.

The basic principles embodied in the two-position switch of FIG. 3 may be extended to switches having more positions. A three-position design is shown in FlGS. 4(a)-4(e). This embodiment defines two switch pairs to which the center position is common. In accordance with the present invention, the three-position embodiment thus employs two solenoids, one for each switch pair. As in the two-position embodiment, blocking of switch progression between switch positions of a pair is accomplished by an associated solenoid and flyback towards home position or the preceding energized position is effected.

The three-position embodiment depicted in FIGS. 4(a)-4(e comprises switch positions identified as OFF, CWS, and CMD, respectively. These positions might correspond to an autopilot control modes where OFF represents complete autopilot disengagement, CWS corresponds to control wheel steering operational mode and CMD refers to command mode. In this type of usage the switch is particularly useful in meeting the fail-safe requirements for logically controlling the initiation and maintenance of control functions.

Control wheel steering might be defined as a lesser sophisticated or involved control function than that of the command function. For example, control wheel steering generally employs force sensors associated with the control stick. Application of a predetermined force to the stick in pitch or bank feeds appropriate voltages to servos to move control surfaces in a manner similar to power steering and include synchronization by means of which aircraft attitudes existing at the cessation of force application are maintained. This control function is of lesser sophistication than the command function which may included selected course maintenance selected vertical profiles, etc.. computed from additional input parameters. With these two modes available it would be desireable that engagement in the control wheel steering mode be prevented unless proper operations as determined by the monitors of this mode is experienced. Should the additional computer circuitries and the input parameters associated with the more sophisticated command function indicate that this function is inoperable, it would be desirable to permit engagement into an operable control wheel steering mode but prevent engagement into the command function. Further, when in either of the engaged modes the monitor associated with that mode indicates failure, it would be desirable that the modes automatically switch back towards OFF position. As in the two-position embodiment, progressive engagement to command functions away from the home position depends upon the logic associated with the position into which the switch is to be placed pennitting such engagement.

The three-position embodiment depicted in FIGS. 4(a)-4(e is accordingly an extension of the concept of the previously described two-position switch. Since three positions are to be involved, two control solenoids are employed, one for each pair of switch positions to which the center position is common.

With reference to FIG. 4(a) the switch comprises a control plate 48 rotatable about a pivot axis 16 by means of a manually positionable handle 12. The plate 48 is keyed to the rotar of a rotary switch which in turn controls mode operation of a controlled device 55. Device 55 includes an engage logic monitoring section 56 from which solenoid energizing power is applied on line 57 TO selectively energize a first solenoid 40 associated with the OFF-CWS switch position pair. A further line 58 selectively applies energizing power to a second solenoid 41 associated with the CWS-CMD switch position pair. In the unenergized states each of the solenoids 40 and 41 positions its associated plunger 43 or 44 into an extended position as illustrated for plunger 44 associated with the command solenoid 41 of FIG. 4(a). Each of the solenoids includes an internally contained return spring such as spring 42 illustrated for solenoid 41 by means of which the solenoid plunger is urged into an extended position in absence of energization of the associated coil. When either of the solenoids 40 or 41 is energized, the plunger associated therewith is magnetically withdrawn as illustrated by the position of plunger 43 associated with solenoid 40 in FIG. 4(a).

Control plate 48 is formed with an arcuate through-slot 45. Ramplike protrusions 49 and 50-52 extend from one side of slot 45 and a ramplike protrusion 51 extends from the other side of the slot. Solenoid plungers 43 and 44 are slotted and fitted with respective cross pins 46 and 47 to form clevislike relationships with the through-slot 45. The respective energized or deenergized positions of the solenoid plungers then determine particular cooperative engagements between the solenoid plunger cross pins and the ramplike protrusions extending from the slot sides. In addition, a first catch or dog member 53 extends from the surface of control plate 48 to provide a positive mechanical blockage for rotation of the switch from the OFF to the CWS position should the CWS solenoid 40 be in deenergize position with plunger extended. A second catch or dog member 54 extends from the surface of the control plate 48 such that rotation of the switch from the CWS to the CMD position is mechanically blocked when solenoid plunger 44 associated with command solenoid 41 is in extended position. Each of the ramplike protrusions provides, by its cooperation with the respective solenoid plunger cross pin members, either a particular camming or an overridable detent function.

Operation of the three-position embodiment depicted in FIGS. 4(a)-4(e) may be described by considering sequential position progressions under various solenoid enetgization states from the OFF position of FIG. 4(a) through the intermediate CWS position to the CMD position illustrated in FIG. 4(e). The relative switch position and solenoid energization states illustrated for the solenoid pair in FlGS-.4(a)-4(e) are chosen for illustrative purposes and do not show all possible noids at any time might be in any one of its two possible positions.

In operation the three position switch may not be moved from OFF position to the CWS position if the CWS logic controlled solenoid 40 is deenergized. with reference to FIG. 4(b) the CWS solenoid 40 return spring then urges the solenoid plunger 43 outward away from the solenoid, and progression of the switch from OFF to CWS is blocked since the CWS catch or dog member 53 on plate 48 moves into a blocking encounter with the end of plunger 43.

In operation the tree position switch may not be moved from OFF position to the CW S position if the CWS logic controlled solenoid 44) is deenergized. With reference to FIG. 4(b the CWS solenoid 40 return spring then urges the solenoid plunger 43 outward away for the solenoid, and progression of the switch from OFF TO CWS is blocked since the CWS catch or dog member 53 on plate 48 moves into a blocking encounter with the end of plunger 43.

When solenoid 40 is energized, plunger 43 is pulled inwardly as depicted in FIG. 4(a), and allows progression of the control plate 48 past the CWS catch 53, over ramp 49 and into the CWS position as depicted in FIG. 4(0). The CWS position held by the detent action between the plunger cross pin 46 and the steeply inclined surface of ramp 49.

If the command solenoid 41 is unenergized, as depicted in FIG. 4(d), the command catch or dog member 54 on plate 48 is moved to encounter the end of the command solenoid plunger 44 as the switch progresses from CWS to CMD position, and this progression is accordingly blocked.

When the command solenoid 41 is energized, progression from the CWS position of FIG. 4(c) to the command position of FIG. 4(e) is permitted as the pin 47 through solenoid plunger 44 rides over ramp inclined surface 52 into a detented command position.

The above described operation illustrates that progression from OFF to successive command positions is possible only if the solenoid associated with the pair of switch positions through which progression is to be effected is energized. Thus, engagement into an operational mode is not possible unless the engage logic associated with that mode indicates operability and the appropriate control solenoid is energized.

Fail-safe operation of the three-position switch is further evidenced by the following considerations.

If the switch is in the center or CWS position as depicted in FIG. 4(0) and the CWS solenoid 40 is deenergized while the switch is in this position, the CWS solenoid 40 releases its plunger 43 such that the cross pin 46 disengages with ramp 49. The return spring 13 rapidly snaps the switch back to the OFF position depicted in FIG. 4(a).

If the switch should be in the CMD position as depicted in FIG. 4(e) and both the CWS and CMD solenoids are deenergized as by complete power failure or complete inoperability of the associated controlled device in either mode, both solenoids release, and the switch snaps under the return force of spring 13 through the center position to the OFF position.

Further operation capabilities of the switch embodiment are a manual override feature. The ramplike protrusions in the control plate slot may be appropriately designed such that a predetermined force on the switch handle 12 may overpower the holding forces developed by the solenoid plunger cross pins on their appropriate rams when the switch is in any one of the possible engage positions.

A further feature of the switch provides a positively detented yet overridable center position. As depicted in FIG. 4(0) a center position detent is realized by the cooperation between the cross pins on the two solenoid plungers and the ramps. When the command solenoid 41 is energized (solid line position), detent action takes place between the respective solenoid cross pins 46 and 47 and ramp surface 49 and 50,

respectively. Should command solenoid 41 be deenergized, detent action is maintained by the cooperation between cross pin 47 of solenoid plunger 44 and ramp 51 (dashed line position of plunger 44).

The present invention has been described in two and threeposition embodiments. The addition of an appropriate number of solenoids with the appropriately formed and located protruding ramps with which the solenoid plunger pins cooperate provides adaptability of the concept for solenoidheld switch applications requiring more than three positions. In general one solenoid is employed for each pair of switch positions and each solenoid so employed doubles in function to provide both fail-safe blocking and latching functions.

The present invention is thus seen to provide improved failsafe multiposition switch means employing magnetic blocking and latching functions by a flexible design concept readily adaptable to changing design criteria and switching requirements.

Although the present invention has been described with respect to particular embodiments thereof, it is not to be so limited as changes may be made therein which fall within the scope of the invention as defined in the appended claims.

I claim:

1. A multiposition magnetically held fail-safe rotary switch having a home position and at least one progressive position to which said switch is positionable, comprising spring means urging said switch means into said home position, control plate means mounted transverse of the rotational axis of said switch shaft, said control plate means comprising a plurality of stop means, a selectively energizable solenoid member including an actuator plunger individually associated with each pair of progressive positions of said switch including said home position, said solenoid-actuating plunger being spring loaded into a first position and positionable between said first and a second position by energization of an associated energizing coil, each said solenoid actuator plunger in each of the positions thereof effecting a predetermined locking engagement with said control plate stop means for predetermined angular positions thereof, said predetermined locking engagements permitting progressive positioning of said switch from said home position to successive positions thereof when the solenoid member between the instant and successive position is energized to place its associated actuating plunger in the second position thereof, said stop means being configured such that the deenergization of the solenoid associated with any one of the successive position pairs of said switch means effects a flyback of said switch toward said home position to the immediately preceding one of said switch positions for which a solenoid associated with said immediately preceding one and a still further preceding one of said switch positions is energized, and effects a flyback of said switch from any one of said progressive positions to said home position when the solenoids associated will all preceding ones of said switch position pairs are deenergized.

2. A switch as defined in claim 1 wherein said plurality of stop means provides a nonoverridable mechanical latch as concerns progression to switch positions away from home position between pairs of which an associated solenoid is unenergized, and provides a manually overridable mechanical latch for switch position progressions towards said home position.

3. A switch as defined in claim 2 wherein the solenoid individually associated with each of said respective successive pairs of switch positions is energized in response to a predetermined logic associated with that switch position of the pair which is the higher progression from said home position.

4. A switch as defined in claim 2 wherein said control plate stop means comprises an arcuate through-slot formed therein, a plurality of ramplike protrusions extending from the edges of said slot, said solenoid plungers being formed with a transverse pin means extending through said slot and engageable with said ramplike protrusions on one side of said slot for a first position thereof and with the protrusions on the other side of said slot for a second position thereof. said first and second positions being effected by respective energized and unenergized states of the associated solenoid.

5. A switch as defined in claim 4 wherein said ramplike protrusions are formed of first and second inclined plane surfaces one of which presents a latching engagement with the transverse pin means of said solenoid plunger and the other of which presents a camming surface overridable to the spring means biasing said plate into said home position.

6. A switch as defined in claim 5 wherein the solenoid individually associated with each of said respective successive pairs of switch positions is energized in response to a predetermined logic associated with that switch position of the pair which is the higher progression from said home position.

7. Switch means as defined in claim 6 wherein said control plate is rotatable by handle means extending coplanar therewith, the mechanical advantage of said handle means permitting manual mechanical override of said latching engagements for switch position progressions towards said home position.

8. Switch means as defined in claim 7 wherein each said solenoid plunger is formed with a longitudinally extending slot within which said control plate is received, each said plunger transverse pin means extending through the sides of said plunger and received within the confines of the arcuate through-slot in said control plate.

9. Switch means as defined in claim 4 wherein said control plate stop means further comprises mechanical catch members extending from the surface thereof to provide a locking engagement with the ends of said solenoid plunger to prevent progression away from said home position from one switch position to a next successive switch position of a given switch pair when the solenoid associated with the given switch pair is unenergized.

10. A switch as defined in claim 9 wherein the solenoid individually associated with each of said respective successive pairs of switch positions is energized in response to a predetermined logic associated with that switch position of the pair which is the higher progression from said home position.

11. Switch means as defined in claim 10 wherein said control plate is rotatable by handle means extending coplanar therewith, the mechanical advantage of said handle means permitting manual mechanical override of said latching engagement for switch position progressions towards said home position.

12. Switch means as defined in claim 11 wherein each said solenoid plunger is formed with a longitudinally extending slot within which said control plate is received, each said plunger transverse pin means extending through the sides of said plunger and received within the confines of the arcuate through-slot in said control plate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 134614.686 Date October l9,l97l

Inventor(s) DaVld W. EH15 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l line 44, delete "oil and substitute therefor "coil"; line after "a" insert -manuall y--; Column 2, line 6, delete "sixth" and substitute therefor --switch--; line 70, delete "means" and substitute therefor --mean--; Column 3, line 23, after "between" insert --the-;

line 29, change "the" (second occurrence) to -The--; line 30, before "path" delete "The" and insert --air gap between the oles and provides a--; line 31, change "(Fig. l to read --(Fig. l(b) line 36,

delete "and" and substitute therefor -to--; line 36, after "with" insert --the--; Column 4, line 62, delete "production" and substitute therefor --protrusion--; Column 5, line 5, delete and substitute therefor --Figure--; line 54, delete line 72, delete "included" and substitute therefor --include--; Column 6, line l8, delete Column 7, line 2, delete "by" and substitute therefor -realized--; lines l5-22, delete in their entirety (this is a duplication of the preceding paragraph); line 27, before "held" insert --is--; line 65, delete "rams" and substitute therefor --ramps-- Signed and s ealed this 1 1 th day of April 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents RM P0 1050110 6 USCOMM-DC wave-pas 

1. A multiposition magnetically held fail-safe rotary switch having a home position and at least one progressive position to which said switch is positionable, comprising spring means urging said switch means into said home position, control plate means mounted transverse of the rotational axis of said switch shaft, said control plate means comprising a plurality of stop means, a selectively energizable solenoid member including an actuator plunger individually associated with each pair of progressive positions of said switch including said home position, said solenoid-actuating plunger being spring loaded into a first position and positionable between said first and a second position by energization of an associated energizing coil, each said solenoid actuator plunger in each of the positions thereof effecting a predetermined locking engagement with said control plate stop means for predetermined angular positions thereof, said predetermined locking engagements permitting progressive positioning of said switch from said home position to successive positions thereof when the solenoid member between the instant and successive position is energized to place its associated actuating plunger in the second position thereof, said stop means being configured such that the deenergization of the solenoid associated with any one of the successive position pairs of said switch means effects a flyback of said switch toward said home position to the immediately preceding one of said switch positions for which a solenoid associated with said immediately preceding one and a still further preceding one of said switch positions is energized, and effects a flyback of said switch from any one of said progressive positions to said home position when the solenoids associated will all preceding ones of said switch position pairs are deenergized.
 2. A switch as defined in claim 1 wherein said plurality of stop means provides a nonoverridable mechanical latch as concerns progression to switch positions away from home position between pairs of which an associated solenoid is unenergized, and provides a manually overridable mechanical latch for switch position progressions towards said home position.
 3. A switch as defined in claim 2 wherein the solenoid individually associated with each of said respective successive pairs of switch positions is energized in response to a predetermined logic associated with that switch position of the pair which is the higher progression from said home position.
 4. A switch as defined in claim 2 wherein said control plate stop means comprises an arcuate through-slot formed therein, a plurality of ramplike protrusions extending from the edges of said slot, said solenoid plungers being formed with a transverse pin means extending through said slot and engageable with said ramplike protrusions on one side of said slot for a first position thereof and with the protrusions on the other side of said slot for a second position thereof, said first and second positions being effected by respective energized and unenergized states of the associated solenoid.
 5. A switch as defined in claim 4 wherein said ramplike protrusions are formed of first and second inclined plane surfaces one of which presents a latching engagement with the transverse pin means of said solenoid plunger and the other of which presents a camming surface overridable to the spring means biasing said plate into said home position.
 6. A switch as defined in claim 5 wherein the solenoid individually associated with each of said respective successive pairs of switch positions is energized in response to a predetermined logic associated with that switch position of the pair which is the higher progression from said home position.
 7. Switch means as defined in claim 6 wherein said control platE is rotatable by handle means extending coplanar therewith, the mechanical advantage of said handle means permitting manual mechanical override of said latching engagements for switch position progressions towards said home position.
 8. Switch means as defined in claim 7 wherein each said solenoid plunger is formed with a longitudinally extending slot within which said control plate is received, each said plunger transverse pin means extending through the sides of said plunger and received within the confines of the arcuate through-slot in said control plate.
 9. Switch means as defined in claim 4 wherein said control plate stop means further comprises mechanical catch members extending from the surface thereof to provide a locking engagement with the ends of said solenoid plunger to prevent progression away from said home position from one switch position to a next successive switch position of a given switch pair when the solenoid associated with the given switch pair is unenergized.
 10. A switch as defined in claim 9 wherein the solenoid individually associated with each of said respective successive pairs of switch positions is energized in response to a predetermined logic associated with that switch position of the pair which is the higher progression from said home position.
 11. Switch means as defined in claim 10 wherein said control plate is rotatable by handle means extending coplanar therewith, the mechanical advantage of said handle means permitting manual mechanical override of said latching engagement for switch position progressions towards said home position.
 12. Switch means as defined in claim 11 wherein each said solenoid plunger is formed with a longitudinally extending slot within which said control plate is received, each said plunger transverse pin means extending through the sides of said plunger and received within the confines of the arcuate through-slot in said control plate. 